I have a 1986 Brat, EA81 w/Hitachi carb, 4spd D/R, accel coil, non-factory exhaust (2" from cat back). It has suddenly begun sounding like an old VW Beetle. Have looked at both intake and exhaust systems but can't find any leaks. Possibly carb throttle shaft? No real change in MPG but seems sluggish now (dragging 2 anchors instead of just one). What to look at?

I am not a master, but it sounds to me based on the sudden onset and the description of the problem that you have a restriction (not a leak) in the exahust. Possibly caused by an interior piece of Cat Converter breaking loose and jaming inside the exahust pipe/muffler.

Just a thought.

i vote for a bad catalytic converter too. you might double check for a bad exhaust manifold gasket. check your air filter too, why not.

I vote for a failed Air Suction Valve. Be careful, as you have likely sucked molten plastic into the carb - this coule explain the slight sluggishness that you feel. Sometimes the plastic can really mess stuff up, and others it just gets stuck in the air box, or in the top of the carb. I had a peice of plastic stick my choke open, and I couldn't start it because of this. The plastic "silencers" attached to the ASV melt on the bottom (hard to see unless you remove them for a look), and without the silencer things get VERY loud.....

 

GD

I'm with GD on the Air Suction Valve. Do a search in the archives; there's lots written about it.

Thanks for the ideas on where to look. Checked exhaust flow at tailpipe...no different than normal. Checked air cleaner housing and noticed pulsing flow from drivers side ASV line with similar (but not as much) flow from passenger side. Flow was from ASV's to air cleaner. No plastic bits in carb or air cleaner. Possible ASV's going bad but not dead yet? Did a search and learned about blocking ASV pipes with a quarters. Just got done doing that and will see how it does.

 

Since there was some flow from the exhaust to the air cleaner/carb, the sudden sluggishness might be due to having what amounts to a second EGR valve dumping exhaust into the fuel mix. Just my thoughts.

Turns out I DID have exhaust leaks. One tiny one just before the converter and the muffler inlet finally rusted thru. Had both repaired and now back to normal. I may still go ahead and replace the ASV's since I didn't like that pulse of exhaust gas into the air cleaner.

Do a search of the archives. ASV from the dealer is in the $75 price range if I remember correctly. You can buy the reed switch portion which is the working part for $18 and just replace that portion alone for the repair. I remember that being written up quite well but can't remember the part numbers.

Yeah - There was a recall in like 82 for the vacuum operated AIS valve's (used on the feedback carb models). The reed portion of the valve is the same as the non-vacuum operated type. Because of the recall, I think they are like $25 or something. You can then replace the parts in your old one that are bad using the parts from the new one as Ed sugested. Also - since you only need these to pass emmissions, and since the quarters are easy to remove and install, I just leave them in all the time unless I'm getting tested. This way the valve is not functioning, and thus will basically never fail again.

 

GD